The Kinetic Model And The Technology Optimization Of HEGF Process

The theoretical research deficiency of the key elements to High Energy Gas Fracture (HEGF) system has greatly restricted its further popularity and application in oilfield. First, the dynamic models and relative solution methods of the three major subsystems, including deflagrating powder loading, liquid column movement above the powder gas and fracture dynamic extension are studied. Based on the powder combustion rate model, the powder deflagrating load model is built using the ideal gas state equation, mass conservation equation and energy conservation equation. On the assumption that there exists a complete contact interface between the powder gas and the liquid column above, the liquid column movement model constituted by continuity equation, momentum conservation equation and energy conservation equation is established, which can take into consideration of the effect of liquid column's kinetic energy distribution and string friction. By coupling the five sub models such as perforation releasing, liquid pressure distribution in fracture, liquid seepage around fracture plane, fracture extension criteria and fracture shape calculation, the fracture extension model is built utilizing mass conservation theory and energy conservation theory. At the same time, based on the improvement of the stress distribution model of casing perforated well considering within the wellbore pressure effect, the limit pressure calculation models which can guarantee casing safe and oil layer's easily cracking is established by theoretical study and the rock shocking damage experiments separately, which can afford a joint qualification for the HEGF's subsystems coupling. And the casing safe checking model can take into consideration of casing wall radial displacement and perforation effect in the process of casing pressuring.And the rock cracking pressure model under Strong dynamic loading condition is a high accuracy relational expression among dynamic fracturing pressure, static fracturing pressure and loading rate, which is regressed according to the rock impact damage experiments to small scale simulation wellbore, using the"rock dynamic damage simulation experimental device". On the basis of the established and improved models of all subsystems and their joint qualifications to HEGF process, the mass conservation equations and energy conservation equations which are correlated by pressure and temperature of all subsystems are built, and then combing the resolving methods of all sub models, the whole process couple calculating technology is formed and the related software is programmed. According to the calculating technology and the application software, the reasonable powder charge bound can be quantitatively calculated and the deflagrating pressure and the fracturing patterns under different parameters values can be accurately predicted. Based on this, the dynamic changes of the three subsystems to the HEGF process are studied, and the sensitivities to fracturing effect of five key parameters including powder structure, powder amount, height of liquid column above the powder gas, perforation density and perforation diameter are analyzed. Finally, the parameters optimization design and the application results of an oilfield HEGF well show that the HEGF system dynamic model and related application software given by this dissertation have strong applicability and accuracy, which can support the HEGF's further popularization and application.